U.S. patent number 7,558,496 [Application Number 11/701,418] was granted by the patent office on 2009-07-07 for image forming device.
This patent grant is currently assigned to Kyocera Mita Corporation. Invention is credited to Akihiro Watanabe.
United States Patent |
7,558,496 |
Watanabe |
July 7, 2009 |
Image forming device
Abstract
A developer agitation screw is provided with a blade to gather
developer onto the sensor surface of a toner concentration sensor.
A toner concentration control unit detects the maximum value of the
output of the toner concentration sensor within each predetermined
period of time, the predetermined period of time being longer than
the period in which developer is gathered on the sensor surface of
the toner concentration sensor by the blade. The obtained maximum
value is used as a characteristic value to control the toner
concentration.
Inventors: |
Watanabe; Akihiro (Nara,
JP) |
Assignee: |
Kyocera Mita Corporation
(Osaka, JP)
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Family
ID: |
38428299 |
Appl.
No.: |
11/701,418 |
Filed: |
February 2, 2007 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20070196116 A1 |
Aug 23, 2007 |
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Foreign Application Priority Data
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Feb 20, 2006 [JP] |
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2006-042909 |
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Current U.S.
Class: |
399/62; 399/258;
399/30; 399/58 |
Current CPC
Class: |
G03G
15/0893 (20130101); G03G 15/0853 (20130101); G03G
2215/0897 (20130101) |
Current International
Class: |
G03G
15/10 (20060101); G03G 15/08 (20060101) |
Field of
Search: |
;399/27,30,53,58,61-63,254,258 ;118/689,690 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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10-186833 |
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Jul 1998 |
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JP |
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2001-354864 |
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Dec 2001 |
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JP |
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Primary Examiner: Ham; Seungsook
Assistant Examiner: Gonzalez; Milton
Attorney, Agent or Firm: Global IP Counselors, LLP
Claims
What is claimed is:
1. An image forming device, comprising: an image carrier; a
developing device being configured to develop electrostatic latent
images formed on said image carrier using developer including
carrier and toner, said developing device having a developing
roller being configured to supply toner to said image carrier, and
a first developer agitation screw being configured to agitate said
developer and to transport said developer to said developing
roller, said first developer agitation screw having a blade; a
toner supply device being configure to supply toner to said
developing device; a toner concentration sensor being configure to
measure toner concentration within said developing device, said
blade being configured to gather developer onto said concentration
sensor at a first predetermined period of time; and a toner
concentration control unit being configure to control said toner
supply device based on the output of said toner concentration
sensor, said toner concentration control unit being configured to
detect a maximum value of said output of said toner concentration
sensor during a second predetermined period of time being longer
than said first predetermined period of time, and said toner
concentration control unit being configured to control toner
concentration using the obtained maximum value as a characteristic
value.
2. The image forming device according to claim 1, wherein said
developing device further has a second developer agitation screw
being arranged between said first developer agitation screw and
said developing roller.
3. The image forming device according to claim 2, wherein toner is
supplied to said first developer agitation screw by gravity.
4. The image forming device according to claim 3, wherein said
developing device is arranged below said toner supply device.
5. An image forming device, comprising: an image carrier; a
developing device being configured to develop electrostatic latent
images formed on said image carrier using developer including
carrier and toner, said developing device having a developing
roller being configured to supply toner to said image carrier, and
a first developer agitation screw being configured to agitate said
developer and to transport said developer to said developing
roller, said first developer agitation screw having a blade; a
toner supply device being configured to supply toner to said
developing device; a toner concentration sensor being configured to
measure toner concentration within said developing device, said
blade being configured to gather developer onto said concentration
sensor at a first predetermined period of time; and a toner
concentration control unit being configured to control said toner
supply device based on the output of said toner concentration
sensor, said toner concentration control unit being configured to
detect a maximum value of the output of said toner concentration
sensor during a second predetermined period of time being longer
than said first predetermined period of time, and said toner
concentration control unit being configured to control toner
concentration using the average value or the moving average value
of the maximum values obtained during a plurality of periods of
time as a characteristic value.
6. The image forming device according to claim 5, wherein said
developing device further has a second developer agitation screw
being arranged between said first developer agitation screw and
said developing roller.
7. The image forming device according to claim 6, wherein toner is
supplied to said first developer agitation screw by gravity.
8. The image forming device according to claim 7, wherein said
developing device is arranged below said toner supply device.
9. An image forming device, comprising: an image carrier; a
developing device being configured to develop electrostatic latent
images formed on said image carrier using developer including
carrier and toner, said developing device having a developing
roller being configured to supply toner to said image carrier, and
a first developer agitation screw being configured to agitate said
developer and to transport said developer to said developing
roller, said first developer agitation screw having a blade; a
toner supply device being configured to supply toner to said
developing device; a toner concentration sensor being configured to
measure toner concentration within said developing device, said
blade being configured to gather developer onto said concentration
sensor at a first predetermined period of time; and a toner
concentration control unit being configured to control said toner
supply device based on the output of said toner concentration
sensor, said toner concentration control unit being configured to
detect the maximum value and several sensor output values before
and after the maximum value of the output of said toner
concentration sensor during a second predetermined period of time
being longer than said first predetermined period of time, and said
toner concentration control unit being configured to calculate the
average value of the plurality of sensor output values, and to
control toner concentration using the obtained average value as a
characteristic value.
10. The image forming device according to claim 9, wherein said
developing device further has a second developer agitation screw
being arranged between said first developer agitation screw and
said developing roller.
11. The image forming device according to claim 10, wherein toner
is supplied to said first developer agitation screw by gravity.
12. The image forming device according to claim 11, wherein said
developing device is arranged below said toner supply device.
13. An image forming device, comprising: an image carrier; a
developing device being configured to develop electrostatic latent
images formed on said image carrier using developer including
carrier and toner, said developing device having a developing
roller being configured to supply toner to said image carrier, and
a first developer agitation screw being configured to agitate said
developer and to transport said developer to said developing
roller, said first developer agitation screw having a blade; a
toner supply device being configured to supply toner to said
developing device; a toner concentration sensor being configured to
measure toner concentration within said developing device, said
blade being configured to gather developer onto said concentration
sensor at a first predetermined period of time; and a toner
concentration control unit being configured to control said toner
supply device based on the output of said toner concentration
sensor, said toner concentration control unit being configured to
detect the maximum value and several sensor output values before
and after the maximum value of the output of said toner
concentration sensor during a second predetermined period of time
being longer than said first predetermined period of time, to
calculate the average value of the plurality of sensor output
values, and to control toner concentration using the average value
or moving average value of the average values obtained a plurality
of times as a characteristic value.
14. The image forming device according to claim 13, wherein said
developing device further has a second developer agitation screw
being arranged between said first developer agitation screw and
said developing roller.
15. The image forming device according to claim 14, wherein toner
is supplied to said first developer agitation screw by gravity.
16. The image forming device according to claim 15, wherein said
developing device is arranged below said toner supply device.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims priority to Japanese Patent Application No.
2006-042909 filed on Feb. 20, 2006. The entire disclosure of
Japanese Patent Application No. 2006-042909 is hereby incorporated
herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to an image forming device.
More specifically, the present invention relates to an image
forming device such as a photocopier, printer, or the like.
2. Background Information
Normally in an image forming device, an electrostatic latent image
is formed on a photosensitive drum, which is the image carrier.
This electrostatic latent image is developed in a developing device
to become a toner image. The toner image on the photosensitive drum
is transferred onto a recording sheet. Then the toner image that is
transferred onto the recording sheet is fixed onto the recording
sheet by a fixing device.
Some developing devices use a two component developer that includes
carrier and toner. In this type of developing device, when an image
is being formed only toner is consumed, so the mixing ratio of
toner and carrier varies. In order to obtain stable images, it is
necessary to replenish the toner to maintain the mixing ratio of
toner and carrier within a fixed range. Therefore in this type of
developing device, the concentration of toner in the developer is
measured with a magnetic sensor, and the toner is replenished based
on the measured toner concentration.
Conventionally, the toner concentration is measured using the
average value of sensor output voltage of a magnetic sensor as a
characteristic value of sensor output as shown in Japanese Patent
Application Laid-open No. H10-186833. Also, there are magnetic
sensors that measure the minimum value in one period of the sensor
output wave form as shown in Japanese Patent Application Laid-open
No. 2001-354864. However, the method of measuring the toner
concentration disclosed in Japanese Patent Application Laid-open
No. 2001-354864 is valid only for developing devices having a
special agitation member. The method is not valid for developing
devices with the commonly-used screw-shaped agitation member.
In developing devices with the commonly used screw-shaped agitation
member, the bulk density and consistency characteristics of the
developer that is transported varies due to degradation with time
and humidity and other environmental conditions. This also results
in a change in the sensor output of the magnetic sensors. Also,
when it is necessary to change the concentration of toner, the
sensor output of the magnetic sensor also changes.
In these cases the shape of the sensor output wave form has the
period of the agitation transport roller. However, when the sensor
output is changed as referred to above, the sensor output wave form
is not simply changed by shifting the output wave form, the minimum
value of the sensor output wave form does not change, but the
sensor output wave form is changed up to the maximum value.
Therefore, using the average value of sensor output as the sensor
characteristic output value to control the replenishment of toner
does not achieve a stable toner concentration.
In view of the above, it will be apparent to those skilled in the
art from this disclosure that there exists a need for an improved
image forming device. This invention addresses this need in the art
as well as other needs, which will become apparent to those skilled
in the art from this disclosure.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an image
forming device that is capable of obtaining a stable sensor output
characteristic value from the sensor output of the toner
concentration sensor, even when the characteristics of the
developer are varied, or the toner concentration is varied.
An image forming device according to a first aspect of the present
invention includes an image carrier, a developing device, a toner
supply device, a toner concentration sensor, and a toner control
unit. The developing device includes a developing roller that
supplies toner to the image carrier and a developer agitation screw
that agitates the developer and transports the developer to the
developing roller. The developing device develops electrostatic
latent images formed on the image carrier using developer that
contains carrier and toner. The toner supply device supplies toner
to the developing device. The toner concentration sensor measures
the concentration of toner in the developing device. The toner
concentration control unit controls the toner supply device based
on the output of the toner concentration sensor. A blade is
provided on the developer agitation screw to gather the developer
onto the sensor surface of the toner concentration sensor. The
toner concentration control unit detects the maximum value of the
output of the toner concentration sensor within each predetermined
period of time. The predetermined period of time is longer than the
period in which developer is gathered on the sensor surface of the
toner concentration sensor by the blade. The toner concentration
control unit uses the obtained maximum value as a characteristic
value to control the toner concentration.
An image forming device according to a second aspect of the present
invention includes an image carrier, a developing device, a toner
supply device, a toner concentration sensor, and a toner control
unit. The developing device includes a developing roller that
supplies toner to the image carrier and a developer agitation screw
that agitates the developer and transports the developer to the
developing roller. The developing device develops electrostatic
latent images formed on the image carrier using developer that
contains carrier and toner. The toner supply device supplies toner
to the developing device. The toner concentration sensor measures
the concentration of toner in the developing device. The toner
concentration control unit controls the toner supply device based
on the output of the toner concentration sensor. A blade is
provided on the developer agitation screw to gather the developer
onto the sensor surface of the toner concentration sensor. The
toner concentration control unit detects the maximum value of the
output of the toner concentration sensor within each predetermined
period of time. The predetermined period of time is longer than the
period in which developer is gathered on the sensor surface of the
toner concentration sensor by the blade. The toner concentration
control unit uses the average value or the moving average value of
the maximum value obtained over a plurality of times as a
characteristic value to control the toner concentration.
An image forming device according to a third aspect of the present
invention includes an image carrier, a developing device, a toner
supply device, a toner concentration sensor, and a toner control
unit. The developing device includes a developing roller that
supplies toner to the image carrier and a developer agitation screw
that agitates the developer and transports the developer to the
developing roller. The developing device develops electrostatic
latent images formed on the image carrier using developer that
contains carrier and toner. The toner supply device supplies toner
to the developing device. The toner concentration sensor measures
the concentration of toner in the developing device. The toner
concentration control unit controls the toner supply device based
on the output of the toner concentration sensor. A blade is
provided on the developer agitation screw to gather the developer
onto the sensor surface of the toner concentration sensor. The
toner concentration control unit obtains a plurality of sensor
output values that includes the maximum value and several sensor
output values before and after the maximum value of the output of
the toner concentration sensor in the predetermined period of time.
The predetermined period of time is longer than the period in which
developer is gathered on the sensor surface of the toner
concentration sensor by the blade. The toner concentration control
unit calculates the average value of the plurality of sensor output
values, and controls the toner concentration using the average
value as a characteristic value.
An image forming device according to a fourth aspect of the present
invention includes an image carrier, a developing device, a toner
supply device, a toner concentration sensor, and a toner control
unit. The developing device includes a developing roller that
supplies toner to the image carrier and a developer agitation screw
that agitates the developer and transports the developer to the
developing roller. The developing device develops electrostatic
latent images formed on the image carrier using developer that
contains carrier and toner. The toner supply device supplies toner
to the developing device. The toner concentration sensor measures
the concentration of toner in the developing device. The toner
concentration control unit controls the toner supply device based
on the output of the toner concentration sensor. A blade is
provided on the developer agitation screw to gather the developer
onto the sensor surface of the toner concentration sensor. The
toner concentration control unit obtains a plurality of sensor
output values that includes the maximum value and several sensor
output values before and after the maximum value of the output of
the toner concentration sensor in the predetermined period of time.
The predetermined period of time is longer than the period in which
developer is gathered on the sensor surface of the toner
concentration sensor by the blade. The toner concentration control
unit calculates the average value of the plurality of sensor output
values, and controls the toner concentration using as a
characteristic value the average value of the average values or the
moving average value obtained over a plurality of periods of
times.
According to the present invention it is possible to obtain a
stable sensor output characteristic value from the sensor output of
the toner concentration sensor, even when the characteristics of
the developer are varied, or the toner concentration is varied.
These and other objects, features, aspects, and advantages of the
present invention will become apparent to those skilled in the art
from the following detailed description, which, taken in
conjunction with the annexed drawings, discloses a preferred
embodiment of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
Referring now to the attached drawings which form a part of this
original disclosure:
FIG. 1 is a view of a diagram of the configuration of a
photosensitive drum and developing device within a photocopier in
accordance with a preferred embodiment of the present
invention;
FIG. 2 is a cross-section view showing the developing device;
FIG. 3A is an isometric diagrammatical view provided to explain the
installation structure of a blade in a first agitation screw of the
developing device;
FIG. 3B is an isometric diagrammatical view provided to explain the
installation structure of the blade in the first agitation
screw;
FIG. 4 is a schematic diagrammatical view showing developer
concentrating on the sensor surface of a toner concentration sensor
of the developing device due to the blade installed on the first
agitation screw; and
FIG. 5 is a diagrammatical view showing a wave form as an example
of the output wave form of the toner concentration sensor.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Selected embodiments of the present invention will now be explained
with reference to the drawings. It will be apparent to those
skilled in the art from this disclosure that the following
descriptions of the embodiments of the present invention are
provided for illustration only and not for the purpose of limiting
the invention as defined by the appended claims and their
equivalents.
The following is an explanation of the embodiments of the present
invention with reference to the drawings for the case of
application to a photocopier.
FIG. 1 is a diagrammatical view showing a photosensitive drum and a
developing device within a photocopier in accordance with a
preferred embodiment of the present invention.
In FIG. 1, 10 is a photosensitive drum (image carrier), and 20 is a
developing device that develops electrostatic latent images formed
on the photosensitive drum 10 using toner.
As shown in FIGS. 1 and 2, the developing device 20 includes a
housing 21 that houses a two component developer that includes
carrier and toner. Within the housing 21, a first agitation screw
22, a second agitation screw 23, and a developing roller 24 are
disposed parallel to the photosensitive drum 10. In other words,
their respective axes of rotation are parallel to one another. The
developing roller 24 includes a developing sleeve and a magnetic
roller within the developing sleeve. A partition wall 21a is
provided between the first agitation screw 22 and the second
agitation screw 23.
By rotating the first agitation screw 22 in a predetermined
direction by a drive device that is not shown in the drawings, the
developer is agitated and transported in the direction indicated by
the arrow A in FIG. 2. By rotating the second agitation screw 23 in
a predetermined direction by a drive device that is not shown in
the drawings, the developer is agitated and transported in the
direction indicated by the arrow B in FIG. 2, which is preferably
opposite to the direction of the arrow A. The layer thickness of
the developer that is transported to the developing roller 24 by
the first agitation screw 22 and the second agitation screw 23 is
regulated by a doctor blade 25 and supplied to the developing
roller 24. Then the developer is supplied to the photosensitive
drum 10 from the developing roller 24.
A toner supply aperture 21b is formed in the wall of the housing 21
of the developing device 20 above the first agitation screw 22. A
toner supply device 30 is provided above the aperture 21b. Toner is
housed within the toner supply device 30. Also, a toner
replenishment screw 31 is provided within the toner supply device
30 to replenish the developing device 20 with toner. Thus, toner
can be supplied to the developing device 20 in part by gravity. The
toner replenishment screw 31 is rotated by a motor 40, so that
toner within the toner supply device 30 is transported into the
developing device 20.
A toner concentration sensor 50 that measures the toner
concentration within the developing device 20 is provided at a
predetermined location below the first agitation screw 22. A
magnetic sensor may be used as the toner concentration sensor 50.
The sensor output of the toner concentration sensor 50 is
transmitted to a control unit (toner concentration control unit)
60. The control unit 60 measures the toner concentration within the
developing device 20 based on the sensor output of the toner
concentration sensor 50. If the measured toner concentration is
lower than a threshold, the motor 40 is driven to supply toner from
the toner supply device 30 to the developing device 20.
As shown in FIGS. 1 and 2, a blade 100 is installed on the first
agitation screw 22 in a position corresponding to the toner
concentration sensor 5 to gather the developer on the sensor
surface of the toner concentration sensor 50. This type of blade
100 is installed on the first agitation screw 22 as follows. The
first agitation screw 22 is made from a shaft and a blade formed in
a spiral shape on the shaft. As shown in FIG. 3A, a plate shaped
blade installation portion 22a is formed integrally on the first
agitation screw 22 in a position corresponding to the toner
concentration sensor 50 between adjacent blades (two blades
separated by one pitch). Also, as shown in FIGS. 3B and 4, the
rectangular shaped blade 100 is fixed to the blade installation
portion 22a. One side of the blade 100 projects from the blade of
the first agitation screw 22.
FIG. 4 shows a view of the developer gathered on the sensor surface
of the toner concentration sensor 50 by the blade 100 installed on
the first agitation screw 22. In FIG. 4, 51 is protective tape that
protects the sensor surface of the toner concentration sensor
50.
The output voltage of the toner concentration sensor 50 becomes a
larger value as the toner concentration becomes lower. As stated
above, the blade 100 is installed on the first agitation screw 22
to gather developer on the sensor surface of the toner
concentration sensor 50, so the sensor output wave form of the
toner sensor 50 is as shown in FIG. 5, for example.
Referring to FIGS. 1 and 5, the output voltage of the toner
concentration sensor 50 increases at the time that developer is
gathered onto the surface of the toner concentration sensor 50 by
the blade 100. Also, at this time more developer is gathered onto
the surface of the toner concentration sensor 50, so at this time
the output voltage of the toner concentration sensor 50 accurately
reflects the toner concentration.
The control unit 60 reads the output voltage of the toner
concentration sensor 50 at time intervals that are very short with
respect to the period T (corresponding to the time interval for one
revolution of the agitation screw 22) in which the developer is
gathered on the surface of the toner concentration sensor 50 by the
blade 100. Also, the maximum value of the sensor output within each
predetermined period of time Ta, which is longer than the period T
in which the developer is gathered on the surface of the toner
concentration sensor 50 by the blade 100, is detected. The obtained
maximum value is used as a characteristic value to control the
toner supply device 30. For example, the obtained maximum value is
compared with a threshold value, and when the maximum value is
larger than the threshold value the toner supply device 30 is
driven to replenish the developing device 20 with toner. In this
way, the characteristic value of the output voltage of the toner
concentration sensor 50 at the time that the developer is gathered
on the surface of the toner concentration sensor 50 by the blade
100 is used. Thus, the toner concentration can be accurately
measured, and highly accurate toner replenishment control can be
carried out. Ta is, for example, set to a time period corresponding
to 1.2 T.
Also, the maximum value of the sensor output within the
predetermined period Ta may be obtained for each predetermined time
period Ta, and every time a predetermined number of maximum values
have been obtained their average value may be calculated and used
as the characteristic value. For example, if the characteristic
value is obtained for every three maximum values, and if the three
maximum values are M1, M2, and M3, then the characteristic value is
(M1+M2+M3)/3.
Also, the maximum value of the sensor output within the
predetermined period Ta may be obtained for each predetermined time
period Ta, and a moving average of a predetermined number of
maximum values may be used as the characteristic value. For
example, in the case where the characteristic value is the moving
average of three maximum values, and the maximum values are
obtained successively as M1, M2, M3, M4, . . . , the characteristic
values are obtained as (M1+M2+M3)/3, (M2+M3+M4)/3, . . . .
Also, the maximum value and several points before and after the
maximum value (for example four points) of the sensor output within
the predetermined period Ta may be obtained for each predetermined
time period Ta, and the average value A of the several sensor
output values calculated. The predetermined period Ta is longer
than the period T in which the developer is gathered on the surface
of the toner concentration sensor 50 by the blade 100. The average
value A obtained may be used as the characteristic value to control
the toner supply device 30.
Also, the average value A of several points in the vicinity of the
maximum value in each predetermined period Ta as described above
may be obtained, and every time a predetermined number of average
values A is obtained, their average value may be calculated and
used as the characteristic value. For example, in the case that a
characteristic value is obtained every time that three average
values A are obtained, and if the three average values are A1, A2,
and A3, then the characteristic value is (A1+A2+A3)/3.
Also, the average value A of several points in the vicinity of the
maximum value in each predetermined period Ta as described above
may be obtained, and the moving average of a predetermined number
of average values A may be used as the characteristic value. For
example, in the case where the moving average of three average
values A is the characteristic value, and if the average values are
successively obtained as A1, A2, A3, and A4, . . . , then the
characteristic values are obtained as (A1+A2+A3)/3,
(A2+A3+A4)/3.
Terms that are expressed as "means-plus function" in the claims
should include any structure that can be utilized to carry out the
function of that part of the present invention.
In understanding the scope of the present invention, the term
"configured" as used herein to describe a component, section or
part of a device includes hardware and/or software that is
constructed and/or programmed to carry out the desired function. In
understanding the scope of the present invention, the term
"comprising" and its derivatives, as used herein, are intended to
be open ended terms that specify the presence of the stated
features, elements, components, groups, integers, and/or steps, but
do not exclude the presence of other unstated features, elements,
components, groups, integers, and/or steps. The foregoing also
applies to words having similar meanings such as the terms,
"including," "having," and their derivatives. Also, the terms
"part," "section," "portion," "member," or "element" when used in
the singular can have the dual meaning of a single part or a
plurality of parts. As used herein to describe the present
invention, the following directional terms "forward, rearward,
above, downward, vertical, horizontal, below, and transverse" as
well as any other similar directional terms refer to those
directions of a image forming device equipped with the present
invention. Accordingly, these terms, as utilized to describe the
present invention should be interpreted relative to an image
forming device equipped with the present invention as used in the
normal riding position. Finally, terms of degree such as
"substantially," "about," and "approximately" as used herein mean a
reasonable amount of deviation of the modified term such that the
end result is not significantly changed. For example, these terms
can be construed as including a deviation of at least .+-.5% of the
modified term if this deviation would not negate the meaning of the
word it modifies.
While only selected embodiments have been chosen to illustrate the
present invention, it will be apparent to those skilled in the art
from this disclosure that various changes and modifications can be
made herein without departing from the scope of the invention as
defined in the appended claims. Furthermore, the foregoing
descriptions of the embodiments according to the present invention
are provided for illustration only, and not for the purpose of
limiting the invention as defined by the appended claims and their
equivalents.
* * * * *